ViewModel
The ViewModel is a core component of the MVVM architectural pattern, serving as a bridge between the view (UI layer) and model (data/business logic layer).
Key Responsibilities
As the central processing unit for views in your application, the ViewModel:
- Manages data flow from models to UI components
- Encapsulates view-specific business logic
- Maintains a clean separation between presentation and domain layers
- Handles component lifecycle and state management
- Provides computed properties and actions for UI interaction
Architectural Role
This implementation leverages MobX's granular reactivity system to:
- Automatically synchronize view updates with ViewModel state changes
- Maintain strict independence between architectural layers
- Enable efficient state propagation through observable properties
- Optimize re-renders using MobX's fine-grained tracking
The ViewModel can serve as a mediator that:
- Abstracts complex data transformations - Formats raw model data for UI consumption
- Handles side effects - Manages async operations and external interactions
- Exposes clean APIs - Provides well-defined interfaces for UI components
- Manages component state - Handles loading, error, and success states
- Controls component lifecycle - Manages mounting, unmounting, and updates
Benefits
The ViewModel pattern delivers:
- Enhanced testability - Verify logic without rendering
- Improved maintainability - Independent layer evolution
- Better collaboration - Parallel work on UI and business logic
- Reusability - Share ViewModels across multiple components
- Type safety - Full TypeScript support with generics
Example
ts
import { ViewModelBase } from "mobx-view-model";
export class CurrentUserBadgeVM extends ViewModelBase<{ userId: string }> {
private userData = /* some data source */
get badgeTitle() {
return `user badge: ${this.userData.fullName || ''}`
}
get isLoading() {
return this.userData.isLoading;
}
}